The prevalence of and risk factors for Atention Deficit Hyperactivity Disorder are being investigated in a population-based study carried out in Johnston County, North Carolina. Through the cooperation of the Johnston County schools, all elementary school age children in the county were studied. With parental permission, teachers completed behavior rating evaluations for children in their classroom. All children classified as potentially having ADHD according to teacher responses or reported by parents to be taking medications were eligible for further study, along with a random sample of all other children. Parent interviews obtained information on child behavior, prenatal and childhood exposures, parental occupational exposures and other factors potentially related to risk for ADHD. The pilot study combined parent and teacher information to estimate the prevalence of ADHD among elementary school children. Two-stage screening used DSM-IV criteria. Teachers completed behavior-rating scales on all children and then parents of potential cases were administered a structured telephone interview. 362 of 424 (85%) children in grades 1-5 in four schools were screened. We estimated the prevalence of medication treatment for attention deficit-hyperactivity disorder (ADHD) among elementary school children in a North Carolina county. We asked parents of 7333 children in grades 1 through 5 attending 17 public elementary schools whether their child had ever been given a diagnosis of ADHD by a psychologist or physician and whether their child was currently taking medication to treat ADHD. Based on results from the first year of the study, according to parental reports, 43 children (12%) previously had been diagnosed with ADHD by a health professional. Thirty-four children (9%) were taking ADHD medication. Forty-six children met study case criteria for ADHD based on combined teacher and parent reports. After adjusting for non-response, the estimated prevalence of treated or untreated ADHD combined was 16% The prevalence estimate based on the full sample is lower, but still greater than published reports based on DSM-IV criteria. In the overall study, parents of 6099 children (83%) provided information on medication use. Of these, 607 children (10%) had been given an ADHD diagnosis, and 434 (7%) were receiving ADHD medication treatment (71% of the diagnosed children were receiving medication). Treatment rates varied by sex, race/ethnicity, and grade. If treatment patterns observed in this study are representative, the public health impact of ADHD may be underestimated. [unreadable] [unreadable] A paperon the psychometric properties of the diagnostic scales used in this population-based effort has been accepted for publication. Acceptance of a second paper is pending final revisions - this paper demonstrates that how the rating scales are characterized and implemented affects the overall prevalence estimates for this disorder and especially the subtype distribution. This has important implications for comparing the results of studies and for interpreting the existing literature on ADHD. We are now working to characterize the overal prevalence of AHDD and identifying pregnancy-related factors as well as environmental exposures (e.g. lead) that may contribute to risk of ADHD. Dr. Rowland (former NIEHS lead investigator) has begun to follow-up the children who were studied to evaluate persistence of symptoms and outcomes among children with various subtypes of ADHD.